In a trial set to begin today, Orlando prosecutors will be pitted against a retired police officer and his family, who say he accidentally fired his gun after his 22-year-old son jumped him during an argument, shooting him twice in the torso and killing him.

Retired cop Timothy Davis' wife and daughter side with him, saying an accidental shooting left Timothy Davis Jr. dead Oct. 1, 2011. But prosecutors say there is evidence suggesting otherwise, with surveillance video of Davis' allegedly retrieving a gun from his car and then aiming it at his son.

"I believe, I believe, I believe my son was shot. In front of my house," Tarsha Davis is heard saying on the 911 call.

As jury selection began Monday, Davis Sr. could be seen in court reading through a bible.

As early as the end of this week, prosecutors are expected to tell the jury that Davis, 48, killed his son in cold blood, and that the two men were arguing about the custody of Davis' grandson when the former cop snapped and shot at his own child.

Defense attorneys say that's not what happened. They say that Davis was defending himself after being tackled by his son.

"In this case, Mr. Davis will have to convince the jury that he acted in self-defense," criminal defense attorney Mark O'Mara said. "If he convinces the jury of that, that would get himself self-defense, which would get him acquitted."

Jurors will most likely also see surveillance video that was captured by the retired officer's own home security system. Investigators say it doesn't show a man struggling with his child, but Davis Sr. looking for his weapon.

"In this case, the video suggests that Mr. Davis Sr. actually pursued or continued the altercation," O'Mara said.

Davis is charged with second-degree murder and could face up to life in prison if convicted. He has pleaded not guilty.